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INTERPRETIVE ANALYSIS OF OBSERVED AND MODELED MESOSCALE OZONE PHOTOCHEMISTRY IN AREAS WITH NUMEROUS POINT SOURCES
Citation:
Pleim, J. AND J.K.S. Ching. INTERPRETIVE ANALYSIS OF OBSERVED AND MODELED MESOSCALE OZONE PHOTOCHEMISTRY IN AREAS WITH NUMEROUS POINT SOURCES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-93/264.
Description:
The Regional Acid Deposition Model (RADM) has been applied to several of the field experiments that were part of the Acid Models Operational and Diagnostic Evaluation Study (Acid MODES) to assess the model's ability to simulate photochemical production of ozone in regions dominated by point source emissions. he comparison of model simulations at different grid resolutions suggests that increased resolution improves the simulation of ozone photochemistry in such regions. urther analysis of NOx, and HOx concentrations and photochemical production rates of ozone, however, show that the model's response to large point source emissions is very unsystematic both spatially and temporally. his is due to the models inability to realistically simulate the small scale (subgrid) gradients in precursor concentrations in and around large point source plumes. ecause of the inherently nonlinear nature of ozone photochemistry with respect to concentrations of NOx and VOC, ozone formation rates in model grid cells depend enormously on grid resolution, dispersion rates (primarily wind speed and mixed layer height), chemical background (VOCs and radicals) and NOx emission rates. hus, the notion that increased grid resolution leads to better simulations of ozone photochemistry is not necessarily true. his analysis points to the need to incorporate some kind of subgrid parameterization of plume photochemistry into mesoscale Eulerian grid models.